Over the course of the last several decades, various methods of suspending prostheses to the residual limb of an amputee were invented. One in particular involved a docking means that included a distal attachment fabricated into the distal end of an elastomeric interface or liner which was rolled onto the residual limb. After the interface was rolled onto the limb, the distal attachment would engage a locking means built into the socket of the prosthesis thereby locking the prosthesis on the patient's limb. This system became a standard in the industry. Manufacturers began producing these interfaces or liners with a fabric layer on the outer surface of the interface to help increase both the durability and ease of insertion into the sockets.
Further advancements were found in suspending the prostheses to a residual limb by creating an airtight seal between the liner mounted on the residual limb of the patient and the socket of the prosthesis to hold the prosthesis on the limb by suction. In some prostheses, one-way expulsion valves were located proximate to the distal end of the socket to expel any remaining air between the liner and the socket and thus create a more effective suspension of the prosthesis. Other prostheses included an evacuation pumping system attached to the distal end of the socket to evacuate the interstitial area between the liner and socket. When the prosthesis is fitted tightly to the limb, the patient feels more secure and perceives the prosthesis to be lighter. A tightly fitted prosthesis gives the amputee the feeling that the prosthesis is more of an extension to the residual limb, not just an addition. In order to enhance the evacuation of air out of the interstitial area of the prostheses, the interface or liner was lined with a fabric on the outer surface thereof to act as a wicking device for the air to travel through and out of the socket. Historically, the liner would have fabric on the external portion of the liner, and these liners are often produced anywhere from 12 inches in length to 20 inches in length. If a below the knee amputee has a limb 6 inches long from the knee joint, the socket would extend the medial and lateral walls a little more proximal, and because of knee flexion the liner may extend another 2-8 inches above the knee. In order to create a seal with the suspension sleeve, the sleeve must extend beyond the liner an additional 2-3 inches to seal against the skin. The added bulk and additional length increase that are associated with this method of using a suspension sleeve to create this suction suspension are two major factors developers have sought for many years to overcome.
To further enhance and maintain the suction created in suspension liners, annular seals have been incorporated into the liners to act as an elastic band around the residuum of the amputee. One example of such a suspension liner is disclosed in U.S. Pat. No. 6,508,842 to Caspers, incorporated herein by reference. Caspers discloses a suspension liner. As best illustrated in FIG. 18, the suspension liner includes urethane liner 92 having an outer fabric cover 130 with an annular seal 140. As disclosed in col. 13, lines 60 and 61, the annular seal is made from the same material as layer 92. As disclosed in col. 14, lines 1-10, the annular seal 140 may be an extension of liner 92 passing through the fabric cover 130. The Caspers invention is typical of a vacuum pumping type suspension system wherein the annular seal 140 acts as an elastic band around the residuum of the amputee. Another example of this type of suspension liner is disclosed in U.S. Pat. No. 8,034,120 to Egilsson, et al. incorporated herein by reference. Egilsson, et al. disclose a suspension liner 310 as best illustrated in FIGS. 45-47 and disclosed in col. 11, line 44 through col. 14, line 26. As disclosed in column 12, lines 41-43, the embodiment of FIGS. 45-47 is similar to the embodiment of FIGS. 43 and 44.The liner includes two tubular textile sections, a first section 312 and second section 314, defining a continuous profile 324. The Klasson patent (U.S. Pat. No. 4,923,474) is referenced in the Egilsson, et al. Patent at col. 5, lines 37-58 as a prior art example of how an outer textile cover is molded to an inner layer of silicone. The Klasson molding technique is applied in the manufacture of the embodiment shown in FIGS. 45-47. The textile sections 312 and 314 (which are comparable to textile sections 212 and 214 of FIGS. 43 and 44) are secured to each other along seam 326. As disclosed in col. 11, lines 49-51, the first material segment 212 of FIGS. 43 and 44 may have stiffness greater than the stiffness of the second material segment 214. This would imply that material segment 312 of FIG. 45 has a greater stiffness than material segment 314. As disclosed in col. 13, lines 44-55, during the molding process, silicone is squeezed through the first material section. As disclosed in col. 13, lines 56-62, this embodiment may include a single layer of silicone instead of the double layers 324 and 326 as shown in FIG. 47. Although material segment 312 has a greater stiffness than segment 314, this does not necessarily mean that the number of stitches per centimeter is greater in segment 312 than in segment 314. Just the opposite is shown. Egilsson et al. also recognize that the profile of the seals is not limited to arcuate or curvilinear, but may be substantially linear as disclosed in col. 12, lines 36-40.
Although the prior art inventions discussed above have benefitted amputees by enhancing the suction effect of the liner to the limb of the amputee, they do have certain drawbacks. One major problem associated with such suspension liners is that the annular seals are restricted by the stiffness of the fabrics extending through the seals during the molding process. Such annular seals are limited in compression and elongation due to the confining embedded fabric and therefore cause the seals to compress the residuum in the adjacent annular region. Horizontal seams stitched across the transverse axis of such prior art to hold different material sections together can also cause compression and discomfort in the residuum. Such prolonged compression actually squeezes the limb thereby inhibiting the flow of blood which leads to irritation not to mention other difficulties especially if the amputee is diabetic, hypertensive, arthritic, etc.
As discussed above, when the prosthesis is fitted tightly to the limb, the patient feels more secure and perceives the prosthesis to be lighter. A tightly fitted prosthesis gives the amputee a more comfortable feeling that the prosthesis is more of an extension to the residual limb, not just an addition. However, the addition of one or several annular seals or seams to the suspension liner inhibiting the flow of blood detracts from such a comfortable feeling especially during the course of a day where the residuum may swell and contract from everyday ambulation.
Maximum comfort is a critical component to the amputee (and consequentially, to their prosthetist) during their search for the correct prosthetic liner. Thus, there is still a need in the art for a prosthetic liner which overcomes the deficiencies of the prior art. As such, the present invention provides a solution to such problems as will be described hereafter.